#include <stdlib.h>

void *bsearch(const void *key, const void *base, size_t nel, size_t width, int (*cmp)(const void *, const void *))
{
    void *try;
    int sign;
    while (nel > 0) {
        try = (char *)base + width*(nel/2);
        sign = cmp(key, try);
        if (sign < 0) {
            nel /= 2;
        } else if (sign > 0) {
            base = (char *)try + width;
            nel -= nel/2+1;
        } else {
            return try;
        }
    }
    return NULL;
}
